scope:

This International Standard specifies methods and procedures for free-field calibration of hydrophones, as well as individual electroacoustic transducers that can be used as hydrophones (receivers) and/or projectors (source transducers). Two general types of calibration are covered within this standard: absolute calibration using the method of three- transducer spherical-wave reciprocity, and relative calibration by comparison with a reference device which has already been the subject of an absolute calibration. The maximum frequency range of the methods described in this standard is from 200 Hz to 1 MHz. The lowest acoustic frequency of application will depend on a number of factors, and will typically be in the range 200 Hz to 5 kHz depending mainly on the dimensions of the chosen test facility, The highest frequency of application for the methods described here is 1 MHz. Procedures for pressure hydrophone calibration at low frequencies can be found in IEC 60565-2 [1]. Procedures for hydrophone calibration at acoustic frequencies greater than 1 MHz are covered by IEC 62127-2 [2]. Excluded from the scope of this standard are low frequency pressure calibrations of hydrophones, which are described in IEC 60565-2 [1]. Also excluded are calibrations of digital hydrophones and systems, calibration of marine autonomous acoustic recorders, calibration of vector sensors such as particle velocity sensors and pressure gradient hydrophones, calibration of passive sonar arrays consisting of multiple hydrophones, and calibration of active sonar arrays consisting of projectors and hydrophones.